Interleukin-6 contributes to chemoresistance in MDA-MB-231 cells via targeting HIF-1α.

Chemoresistance is a critical challenge in the clinical treatment of triple-negative breast cancer (TNBC). It has been well documented that inflammatory mediators from tumor microenvironment are involved in the pathogenesis of TNBC and might be related to chemoresistance of cancer cells. In this study, the contribution of interleukin-6 (IL-6), one of the principal oncogenic molecules, in chemoresistance of a TNBC cell line MDA-MB-231 was first investigated. The results showed that IL-6 treatment could induce upregulation of HIF-1α via the activation of STAT3 in MDA-MB-231 cells, which consequently contributed to its effect against chemotherapeutic drug-induced cytotoxicity and cell apoptosis. However, knockdown of HIF-1α attenuated such effect via affecting the expressions of apoptosis-related molecules as Bax and Bcl-2 and drug transporters as P-gp and MRP1. This study indicated that targeting at IL-6/HIF-1α signaling pathway might be an effective strategy to overcome chemoresistance in TNBC therapy.